1. Field of the Invention
This invention relates generally to clamping mechanisms and, more particularly, the invention relates to devices for clamping a die to a heated platen in a frame-type press.
2. Description of Related Technology
In the manufacture of board products such as hardboard and fiberboard, embossing dies utilized for the board-forming process are typically clamped or otherwise attached to heated platens of a frame-type press. Embossing dies are typically of either one-piece construction or are welded to a carrier plate. Such dies or die and plate combinations may weigh up to 20,000 pounds and have dimensions of up to about 10 feet by 25 feet. The platens may be heated to temperatures greater than 400.degree. F. When a die is subjected to such temperatures, it may undergo considerable thermal expansion, resulting in difficulties in clamping the die to the platen.
A prior known clamping system for attaching a die to a platen includes a plurality of fasteners, spaced about the perimeter of the die and platen, each including a pair of matching slotted ears, a bolt and a nut. One of the slotted ears of each fastener is welded to the platen and the matching slotted ear is welded to the die. The bolt shank is passed through the pair of slotted ears until the bolt head abuts one of the ears and the nut is screwed onto the bolt threads until it abuts against the other ear, thereby securing the die to the platen.
A disadvantage of the fasteners described in the previous paragraph is that initially, the bolts cannot be utilized to attach a cool die to a heated platen because the slotted ears are not in alignment. Temporary fasteners are required to connect additional pairs of slotted ears as the die expands due to heat from the adjacent platen. After full thermal expansion, the temporary fasteners are replaced by the bolts and nuts described above. A further disadvantage of this clamping system is that the bolts and nuts must be installed by hand near the hot platen.